In order to provide for smoother shaves and to increase the comfort of the user, shaving aids in the form of comfort strips have been mounted on disposable razor heads and in disposable razor systems for many years. For example, U.S. Pat. No. 4,170,821, issued to Booth, discloses a solid water soluble shaving aid incorporated as a strip attached to a disposable razor blade cartridge. Razor heads having such comfort strips are currently marketed with the shaving aid being mixed with a thermoplastic polymer and have a uniform, unchanging color and texture.
Generally, individuals with sensitive skin are most likely to be users of razors containing shaving aids. Consequently, many products which are currently marketed with shaving aids contain materials such as aloe and are directed at the sensitive skin user. However, a drawback of currently available comfort strip-type shaving aids is that the strips gradually degrade and, after a certain number of uses, the shaving aid material contained in the strips is reduced to the point that the strips are not effective for the sensitive skin user. At this point a sensitive skin consumer should replace the razor blade cartridge to ensure the continued availability of shaving aid. However, absent a definite indication, many users do not realize when the cartridge should be replaced and consequently the quality of the shave suffers.
Various attempts have been made to create systems to indicate when the user should change the cartridge. Most of the previous systems require the user to manually interact with the razor by an act such as the turning of a knob or the breaking off of a tab. Such systems are inefficient in that most users are not careful to accurately perform the acts necessary to monitor their razor cartridge usage.
It would, therefore, be desirable to provide a disposable razor cartridge or a disposable razor system with a shaving aid which would automatically indicate to the user that the cartridge containing the shaving aid should be replaced. Such shaving aids would not require manual intervention and thus would be more accurate than presently known systems.
It would further be desirable to provide such a shaving aid in the form of a comfort strip which would change color after a certain number of uses to signal to the user that the cartridge should be replaced. The color change may take place either through selective solubility or through abrasion. Such a shaving aid would allow the user to obtain the most efficient cartridge use. It would be particularly desirable to provide a shaving aid which changes color coincidentally with the wear of the blade such that when the strip changes the blade is no longer delivering average optimum performance.